The present invention relates to the use of organic light emitting diodes for area illumination.
Solid-state lighting devices made of light emitting diodes are increasingly useful for applications requiring robustness and long-life. For example, solid-state LEDs are found today in automotive applications. These devices are typically formed by combining multiple, small LED devices providing a point light source into a single module together with glass lenses suitably designed to control the light as is desired for a particular application (see, for example WO99/57945, published Nov. 11, 1999). These multiple devices are expensive and complex to manufacture and integrate into single area illumination devices. Moreover, LED devices provide point sources of light, a plurality of which are employed for area illumination.
Organic light emitting diodes (OLEDs) are manufactured by depositing organic semiconductor materials between electrodes on a substrate. This process enables the creation of light sources having extended surface area on a single substrate. The prior art describes the use of electro-luminescent materials as adjuncts to conventional lighting (for example U.S. Pat. No. 6,168,282, issued Jan. 2, 2001 to Chien). In this case, because of the limited light output from the electro-luminescent material, it is not useful for primary lighting.
EP1120838A2, published Aug. 1, 2001 describes a method for mounting multiple organic light emitting devices on a mounting substrate to create a light source. However, this approach of mounting multiple light sources on a substrate increases the complexity and hence the manufacturing costs of the area illumination light source.
It would also be useful if a light source is compatible with existing lighting infrastructure, for example the common screw-type base (standard E26) and the pin-type bayonet base (standard B22). Moreover, the light source should preferably be readily and safely replaceable by a consumer at minimal cost.
There is a need therefore for an improved, replaceable OLED lighting apparatus having a simple construction using a single substrate, compact, and compatible with the existing lighting infrastructure.
The need is met by providing lighting apparatus that includes: a solid state area illumination light source having, a substrate, an organic light emitting diode (OLED) layer deposited upon the substrate, the organic light emitting diode layer including first and second electrodes for providing electrical power to the OLED layer, an encapsulating cover covering the OLED layer, and first and second conductors located on the substrate and electrically connected to the first and second electrodes and extending beyond the encapsulating cover for making electrical contact to the first and second electrodes by an external power source; and a socket for removably receiving and holding the light source and having first electrical contacts for making electrical connection to the first and second conductors of the light source, and second electrical contacts for making electrical connection to an external power source.
The present invention has the advantage of providing an inexpensive, long lived, highly efficient, light source that is replaceable, compact, and is compatible with existing lighting infrastructure.